Practice questions focused on the Nernst equation, Gibbs free energy, and equilibrium constants to support chemistry exam preparation.
Na⁺ + e⁻ → Na . 1 mol Na (23.5 g) requires 1F. Moles = (1.175/23.5) = 0.05 mol , Charge = 0.05 × 96500 = 4825 C . t = (Q/I) = (4825/2) = 2412.5 s .
Ref: NCERT Class 12 Chemistry > Chapter 2: Electrochemistry > Topic: Nernst Equation and Gibbs Energy and Equilibrium Constant
kappa = (cell constant/R) , 0.0012 = (cell constant/250) , cell constant = 0.3 cm⁻¹ .
Ref: NCERT Class 12 Chemistry > Chapter 2: Electrochemistry > Topic: Nernst Equation and Gibbs Energy and Equilibrium Constant
kappa = (cell constant/R) , 0.00141 = (cell constant/200) , cell constant = 0.282 cm⁻¹ .
Ref: NCERT Class 12 Chemistry > Chapter 2: Electrochemistry > Topic: Nernst Equation and Gibbs Energy and Equilibrium Constant
Ecell = E°cell - (0.059/2) log ([Zn²⁺]/[Cu²⁺]) = 1.10 - (0.059/2) log (0.01/0.1) = 1.129 V .
Ref: NCERT Class 12 Chemistry > Chapter 2: Electrochemistry > Topic: Nernst Equation and Gibbs Energy and Equilibrium Constant
E°cell = (0.059/n) log Kc , 0.96 = (0.059/n) × 32 , n = (1.888/0.96) ≈ 2 .
Ref: NCERT Class 12 Chemistry > Chapter 2: Electrochemistry > Topic: Nernst Equation and Gibbs Energy and Equilibrium Constant
Δr G° = -n F E°cell , -424600 = -n × 96500 × 1.10 . n = (424600/96500 × 1.10) = (424600/106150) ≈ 4 .
Ref: NCERT Class 12 Chemistry > Chapter 2: Electrochemistry > Topic: Nernst Equation and Gibbs Energy and Equilibrium Constant
E°cell = 1.36 - (-0.25) = 1.61 V . Ecell = 1.61 - (0.059/2) log ([Ni²⁺][Cl⁻]²/PCl_₂) = 1.61 - 0.0295 log (0.002 × 0.0025/0.5) = 1.61 + 0.084 = 1.694 V .
Ref: NCERT Class 12 Chemistry > Chapter 2: Electrochemistry > Topic: Nernst Equation and Gibbs Energy and Equilibrium Constant
Δ E = -(0.059/n) log ([H⁺]₂/[H⁺]₁) , 1.17 - 1.23 = -0.06 = -(0.059/n) log (1/0.1) . -0.06 = -(0.059/n) × 1 , n = (0.059/0.06) ≈ 1 , but cathode reaction O₂ + 4H⁺ + 4e⁻ , so n = 4 .
Ref: NCERT Class 12 Chemistry > Chapter 2: Electrochemistry > Topic: Nernst Equation and Gibbs Energy and Equilibrium Constant
Δr G° = -n F E°cell , -169840 = -n × 96500 × 0.88 . n = (169840/96500 × 0.88) = (169840/84920) ≈ 2 .
Ref: NCERT Class 12 Chemistry > Chapter 2: Electrochemistry > Topic: Nernst Equation and Gibbs Energy and Equilibrium Constant
Δr G° = -n F E°cell . -212270 = -2 × 96500 × E°cell , E°cell = 1.1 V .
Ref: NCERT Class 12 Chemistry > Chapter 2: Electrochemistry > Topic: Nernst Equation and Gibbs Energy and Equilibrium Constant
Ecell = E°cell - (0.059/n) log ([Ox]/[Red]) , 0.68 = 0.62 - (0.059/n) log (0.01/0.1) . 0.06 = (0.059/n) × 1 , n = (0.059/0.06) ≈ 1 .
Ref: NCERT Class 12 Chemistry > Chapter 2: Electrochemistry > Topic: Nernst Equation and Gibbs Energy and Equilibrium Constant
E°cell = 1.36 - (-0.25) = 1.61 V . Ecell = 1.61 - (0.059/2) log ([Ni²⁺][Cl⁻]²/PCl_₂) = 1.61 - 0.0295 log (0.001 × 0.01/2) = 1.61 + 0.103 = 1.713 V .
Ref: NCERT Class 12 Chemistry > Chapter 2: Electrochemistry > Topic: Nernst Equation and Gibbs Energy and Equilibrium Constant
